All drawing products used: Prismacolor
Colorless blender pencil:
Once you have your colours in place, use a firm pressure in circular motions to blend the colours together. I rarely use this method as I don't like the finish it gives, it's a personal preference, but it leaves too much of a waxy residue on the surface for my liking.
Colorless blender marker:
Once your colours are in place, use small circular motions to blend the pigments into each other. I honestly never use the marker method, I'm yet to find myself in a situation where I need it. The marker acts as a kind of solvent that mixes the pigment together. For me, the marker doesn't seem to cover enough for the kind of blended look I like to use.
Once your colours are in place, use many light to medium layers while constantly keeping the pencil sharp until desired blending is achieved. Try using small circular motions. Nowadays I mainly use this blending method. I have more blending control when using a sharp pencil, but again that's just my personal preference.
After placing your colours, leave the pencil blunt and use firm pressures and circular motions to blend your colours together. This is a faster way of blending but I feel as though I don't get the level of precision I want. This way also generates more wax build up which I don't like, and you can see the streaky waxy lines on the surface of your drawing.